Ho, every one that thirsteth! Though the mass are gross and carnally minded, there will ever be some who have higher aspirations—who hunger and thirst after righteousness" (Matthew 5:6), and desire spiritual blessings.
These are invited, first of all, to come and partake of the good things provided for them in Messiah's kingdom. Come ye to the waters (on the spiritual symbolism of water, see the homiletics on Isaiah 44:3, Isaiah 44:4).
Here the "peace" and "righteousness" of the Messianic kingdom (Isaiah 54:13, Isaiah 54:14) are especially intended. Our Lord's cry on the last day of the Feast of Tabernacles (John 7:7) is clearly an echo of this.
Wine and milk. These are not symbols of temporal blessings, as many have thought. "Wine, water, and milk are," as Delitzsch says, "figurative representations of spiritual revival, re-creation, and nourishment."
Without money and without price. God's spiritual gifts are freely given to men; they cannot be purchased. Being in their own nature "more precious than rubies," their value transcends human means of payment.
They cannot even be earned by man's best works; for man's best works are comprised in his duty to God, and have, therefore, no purchasing power. God may choose to reward them; but if he does it is of his free grace.